About half of Americans 65 and older complain of arthritis symptoms like joint pain and stiffness. Nearly a third of middle-aged people have arthritis. The number of has been growing, mostly because of overweight baby boomers.

Arthritis can make it harder to balance and it can sap lower-body strength, contributing to falls. Walking and moderate physical exercise is recommended for those with arthritis to keep symptoms from getting worse, said the CDC’s Kamil Barbour, the study’s lead author.

The report is based on a 2012 survey of 339,000 people ages 45 and older.